Casette encapsulating magnetic recording tape

ABSTRACT

A CASSETTE ENCLOSING A MAGNETIC TAPE WHEREIN THE CASSETTE CONTAINS A PLASTIC REGULATING PLATE. THE PLASTIC REGULATING PLATE CONTAINS FINELY DIVIDED PARTICLES DISPERSED THEREIN.

p 1971 GORO AKASHI EI'AL 3,606,303

CASETTE ENCAPSULATING AGNETIC RECORDING TAPE Filed Oct. 13. 1969 United States Patent U.S. Cl. 242-199 Claims ABSTRACT OF THE DISCLOSURE A cassette enclosing a magnetic tape wherein the cassette contains a plastic regulating plate. The plastic regulating plate contains finely divided particles dispersed therein.

BACKGROUND OF THE INVENTION (1) Field of the invention The present invention relates to a cassette enclosing a magnetic recording tape.

(2) Prior art The structure of the conventional magnetic recording tape generally comprises a magnetic recording layer coated on a substrate such as a film support, such as cellulose diacetate, cellulose triacetate, polyethylene terephthalate, or polyvinyl chloride, or on a wire support of a non-magntic metal. This magnetic recording layer (hereinafter referred to as magnetic layer) comprises 'y-Fe O generally of a high hardness of 5 on the mobs scale, dispersed in a binding agent, with the amount of 'y-Fe O used in the magnetic layer being in the range of 70 to 80% by weight. Therefore, the magnetic recording tape not only is a recording material but also, in view of its mechanical properties, can be used as an abrasive. This can be easily seen since dFezog (red iron oxide), resembling the magnetic material in chemical structure, has a hardness of from 5 to 5.5 on the mobs scale and is used as an abrasive.

The composition of newer magnetic recording layers has changed from 'y-FC O' to an alloy comprising a Fe-Co, a Co-Ni, or a Fe-Co-Ni system, or a thin film of an comprising a Fe-Co-Ni system will be used as the magnetic layer itself. Thus, the magnetic layer of the future will be considered to be extremely high in hardness. In addition, the magnetic recording tape is supported by a guide pole of the tape recorder and then transported on the tape recorder. Use of the magnetic recording layer results in abrasion of the guide pole. Of even greater concern is the high speed winding and rewinding operations used in recording and reproduction of the magnetic recording material. In the situations above, the velocity of the recording material in such operations is higher by about 30 times than that encountered in the usual recording and reproducing operations. As a result, the guide pole is abraded to a greater degree at higher speeds. This problem exists with the guide pole as described above, but also with recently developed cassette, enclosing a magnetic recording tape.

3,606,203 Patented Sept. 20, 1971 The attached drawing is a view showing a partially-cut cross-section of a conventional cassette enclosing a magnetic reecording tape.

As shown in the attached drawing, in a cassettee 1, a tape 2 is wound on winding core hubs 3 and 3. A tape regulating plate formed by flexible plastic sheets 4 and 4' is provided in a zone corresponding to the conventional reel flange and the tape 2 is wound from one hub to another hub in the usual operation. In this case, the regulating plates 4 and 4' are fixed, but the hub 3' or 3' rotates with the tape 2. Thus, the regulating plates 4 and 4' are subject to a rubbing force from the edge of magnetic tape and are worn away as with the above-described guide pole. In such cases, the degree of unevenness of the edge of the magnetic tape is much higher than that of the recording surface of a magnetic tape and is known to abrade the flexible regulating plates 4 and 4' due to the high hardness of the magnetic recording layer containing 'y-Fe O e.g. the regulating plate are shaved as if with the blade of a saw.

The materials used for the elements of the instrument contacting the recording surface or the edge of the magnetic tape have been conventionally selected from hard chromium-plated materials, stainless steel, and Teflon, a polyfluorethylene polymer. Teflon has been used as a material for the regulating plate in cassettes. The Teflon sheet has been quite practical. The combination of a Teflon sheet and a Teflon tape is excellent since the frictional resistance of a fixed Teflon sheet and a running tape is low due to the low coefficient of friction of Teflon. However, the endurance of the Teflon sheet has a lifetime of only 200 to 300 windings and rewindings (hereinafter called ductability), and it has been found that, with windings and rewindings above this level, the surface of Teflon becomes very rough. Heretofore, it was thought that the use of a Teflon sheet was impossible since the Teflon sheet is high in frictional electrification due to its high electric resistance of above 10 ohms. Therefore, to counteract this problem, a material containing carbon black has recently been used for reducing the electric resistance. However, this elevated the practical durability of the Teflon sheet to 350 to 400 windings and rewindings only.

DESCRIPTION OF THE INVENTION On consideration of the deterioration in durability in cassettes, it was found that the deterioration is caused by the abrasion resistance of the Teflon itself rather than by the electrification of the Teflon. That is, the abrasion resistance of Teflon theoretically was considered to be very low because its coefiicient of friction was low. However, it was found that the unusual abrasion of Teflon sheets is caused by a lack of hardness and the Teflon sheet is violently abraded due to the unevenness of the edge of the magnetic recording tape.

To solve these known problems, it was found that a Teflon' sheet containing dispersed particles of Cr O A1 0 SiC, or 'y-Fe O and the like, having an average particle size of below 10,11. and a mohs hardness of above 5 has an extremely excellent durability. Thus, the present invention relates to a cassette containing an enclosed magnetic recording tape and at least one regulating plate, in which the regulating plate contacts the side face of the magnetic recording tape during winding. The regulating plate used is a plate containing dispersed finely divided particles, having a hardness of above on the mohs scale, dispersed in the plastic.

The method whereby the particles are added to the TABLE 1 plastic does not require any chemical reaction, but may 5 Add d D be accomplished by mixing and dispersing. In case the Mans, Average g, 5; hardness of the powder or particles to be added to the hardparticle (volunga mmliie plastic of the plate is lower than that of the magnetic Hess pemen es) material used in the tape, its use is less effective. As a lid p wder: 9 0 82 12 1 00o result, the finely divided powder to be added desirably 9 12 1000 should have a mohs hardness of above 5. A powder 3 3% 3,883 having a mohs hardness of above 7 has remarkable 8 12 x1000 durability. In addition, the particle size of the fine powder 0 O 1, 32% used has an important influence upon the ease with which a-reioill 5: 7 1:08 12 590 the plastic heet used in making the regulating plate Can z--,- 7 12 be processed, although not appreciably afiecting durability, Comparative example cassette 0 370 and, as a result, the average particle size to be used 1s From the results Shown in Table 1 above, the cassette preferably d d b enclosing a magnetic recording tape according to the The present mvenuon W111 be 1 ustrate present invention is much higher in durability than that rgference the examples and comparauve examp e of the cassette of the comparative example. From these gwen herem: results, it can be seen that the solid particles used in the present invention should be above 5 in mohs hard- 1e Comparative 6 amp ness. From a practical standpoint, the test of durability was discontinued after a durability of 1000 times had z i 3 'f gi g i been reached. The surface of the Teflon sheet regulating on a PO ye Y e p t plate, containing the particles of above 5 in hardness h kn A it oatin l1 uid 6011123111111" finely t .i magne c c g q 1 according to the present invention, were compared with l fl' P 9 of m avii'rage e the surface of the Teflon sheet regulating plate contain- Slze dlsriersed m the dlrectlin of g g i 2, a ing no added particles after testing for durability. The ageni:1 with th t g i zh fifin gz tg 232 portion of Teflon sheet contacting the edge of the mag- Welg Was 6 on 6 netic tape in the case of the Teflon sheet containing no dry thickness and then was dried. This coated material add d a 1 .Wa {0 d t b r to make a magnetic recording tape of 3.81 mm. p r 1c 1 s o e We n away m Y d about 90 m in len th The ta 6 was ference and, in an extreme case, to be worn out. With W1 an g I P p the Teflon sheets utilizing the particles, little or no abrationed between two flexible sheet-like regulating plates Sion was observed However with the Teflon Sheet Com made of pure Teflon of 50 in thickness in a conventional mining wFezo 5 to 5 5 mobs, hardness about half cassette (Compact Cassette? 3 Cassatt? fanclosmg a magof the abrasioii of the Teflon sheet having no dispersed netic recording tape and sold by PhllllPS Company of particles was Observed Holland). D

The cassette, enclosing a magnetic recording tape and 40 Example H produced as above, was placed in a magnetic tape recording apparatus and the high speed running of the mag- A cassette enclosing a magnetic recording tape was netic tape was tested by repeated high speed wmdmgs prepared in the same manner as in Example I to test the and rewindings at 90 m./70 seconds as the tape running efifect of varying the amount of dispersed particles of velocity. The durability is defined as the number of times above 5 in mohs hardness added to the lastic sheet re ua 1 a p g the tape can be run its entire length 1n less than 180 seclatmg plate. ends or until the tape becomes impossible to run. Table 2 shows the effect of adding Cr 0 of 1.171s in The result was that the number of times the tape could average particle size. Unexpectedly, Cr O was found to be run in less than 180 seconds was 346 repeated ruube effective at a level of only 2%. When the Cr O connings. The tape became impossible to run after 370 retent is more than 2%, a durability of above 1000' times peatings. On opening the cassette and inspecting the reguwas observed. However, if the Cr O content is more lating plate, remarkable scratching was found thereon. than 30%, the ease with which the plastic can be proc- Therefore, from the result measured under such condiessed was poor, and then the test was discontinued.

TABLE 2 Regulating plate material (times of repeating) Delrin (a Teflon (a Nylon Content of ClzOa polyacetal polytetrafiu- (a poly- Polyeth- Polypro- (vol. percent) resin) oroethylene) amide) ylene pylene 450 920 650 540 530 500 1, 000 700 620 580 510 1, 000 820 630 630 670 1,000 1,o0o 640 650 630 1,0o0 900 690 700 640 980 710 740 l Poor proeessebility.

tion, the durability material used as the regulating plate of this cassette is recognized to be about 370 times.

Example I The same cassette enclosing a magnetic recording tape as used in the above Comparative example was made except the material used in the regulating plate was changed. The material used as the regulating plate was Teflon in which solid finely divided particles, as shown in Table l, were dispersed at a volume ratio of 12 per 100 As can be seen from the results shown in Table 2, the durability of various plastics can be remarkably enhanced by the addition of finely divided particles of above 5 in mohs hardness.

What is claimed is:

1. In a cassette comprising an enclosed magnetic recording tape wherein the cassette contains a regulating plate which contacts the edge of a magnetic recording tape during winding, the improvement which comprises a to Teflon was used. The durability lite or the cassette regulating plate which is a lastic plate containing fine y 5 divided particles of above 5 in mohs hardness dispersed therein.

2. The cassette of claim 1 wherein the powdery particles have an average particle size of below 101L- 3. The cassette of claim 2 wherein the plastic plate is prepared from a material selected from the group consisting of polyacetals, polytetra-fluoroethylenes, polyamides, polyethylenes and polypropylenes.

4. The cassette of claim 3 wherein the particles are selected from the group consisting of Cr O A1 0 SiC, tit-F8203 and Slog- 5. The cassette of claim 4 wherein the material is a polytetrafluoromethylene and wherein the particles are CI'2O3.

References Cited UNITED STATES PATENTS LEONARD D. CHRISTIAN, Primary Examiner US. Cl. X.R. 

